In mobile communication systems, a mobile station is notified of information necessary when performing connection setup or necessary during connection, and notified of information on other systems beforehand. This information is called broadcast information (system information).
Broadcast information in IMT 2000 includes a master information block (MIB) and subordinating system information blocks (SIBs).
The master information block includes presence or absence of transmission of the system information block, transmission schedule, and a value (value tag) indicating presence or absence of change of information content. On the other hand, the system information blocks are defined for each type of information having a same property. For example, as the system information blocks, setting information of a common channel and information on restriction are defined as different system information blocks.
In IMT 2000, it is defined that a mobile station originates a call after reading necessary broadcast information before performing call connection. However, transmission schedule of the system information block or the value tag cannot be ascertained unless the master information block is read. Thus, it is at least necessary to read the master information block. For example, since an interleave length of the broadcast information channel in IMT 2000 is 20 ms, the mobile station needs to receive broadcast information at least for 20 ms to read the master information block.